For this case we must raise an inequality.
We have "d" dollars initially and they are spent 12. Then:
[tex]d-12[/tex]
At least 51 dollars remain, then, the sign of inequality is greater or equal in favor of the expression[tex]d-12[/tex], that is:
[tex]d-12\geq 51[/tex]
Resolving:
[tex]d\geq 51 + 12\\d\geq 63[/tex]
There are at least 63 dollars left in the account.
Answer:
[tex]d-12\geq 51\\d\geq 63[/tex]
